The operator of a damaged nuclear plant in north-eastern Japan, is developing a device to eliminate radioactive substances from seawater, a report said Wednesday.

Tokyo Electric Power Co (TEPCO), which runs the Fukushima Daiichi nuclear plant, said the company hoped to place the device in the Pacific Ocean near the plant at the end of May, public broadcaster NHK reported.

Since the plant was hit by a magnitude-9 earthquake and tsunami on March 11, it has leaked radioactive materials into the air and sea.

The operator said it planned to pump contaminated seawater through a metal container filled with zeolite, a mineral that absorbs radioactive materials.

High levels of radiation were measured in the waters around the plant as TEPCO detected 5,800 times the legal limit of radioactive iodine in seawater samples collected near reactor number 2.